Is my 340 Overcarbed? Avg 5-6 MPG

Not enough initial, PERIOD.

You can't see the stop bushing in your picture. It's on the bottom side of all that stuff. Based on the two bushings you have in the "parts" pic, I'm guessing the black 18* is installed.

I wouldn't get rid of any parts just yet. Replacing the carb may not solve any issues.